Golf ball cover compositions

ABSTRACT

The present invention is directed to golf ball cover compositions containing blends of high or low carboxylic acid based copolymers and ethylene copolymers such as ethylene alkyl acrylates. The carboxylic acid groups of the blends are neutralized with metal cations. Golf balls produced with the cover molded thereon exhibit desired properties of distance and high coefficient of restitution without substantially sacrificing and/or improving characteristics like playability and durability when compared to existing covers comprising ionomeric resin blends.

The present application is a continuation of U.S. Application Ser. No.08/551,254 filed on Oct. 31, 1995, now U.S. Pat. No. 5,591,803 which inturn is a continuation of U.S. Application Ser. No. 08/359,620 filed onDec. 20, 1994 now U.S. Pat. No. 5,542,677, and currently copendingherewith.

FIELD OF THE INVENTION

The present invention relates to metal cation neutralized blends of acidcopolymers with non-acid functional polymers such as ethylene acrylates,and to improved golf ball covers made from these blends. The improvedgolf ball covers are useful for producing golf balls, particularlymulti-piece balls, exhibiting essentially the desired travel distancewhile maintaining or improving the playability and/or durabilitycharacteristics necessary for repetitive play.

BACKGROUND OF THE INVENTION

Ionomeric resins are polymers containing interchain ionic bonding. As aresult of their toughness, durability, and flight characteristics,various ionomeric resins sold by E.I. DuPont de Nemours & Company underthe trademark "Surlyn®" and more recently, by the Exxon Corporation (seeU.S. Pat. No. 4,911,451) under the trademarks "Escoro®" and thetradename "Iotek", have become the materials of choice for theconstruction of golf ball covers over the traditional "balata" (transpolyisoprene, natural or synthetic) rubbers. The softer balata covers,although exhibiting enhanced playability properties, lack the durabilityproperties required for repetitive play.

Ionomeric resins are generally ionic copolymers of an olefin, such asethylene, and a metal salt of an unsaturated carboxylic acid, such asacrylic acid, methacrylic acid or maleic acid. In some instances, anadditional softening comonomer can also be included to form aterpolymer. The pendent ionic groups in the ionomeric resins interact toform ion-rich aggregates contained in a non-polar polymer matrix. Themetal ions, such as sodium, zinc, magnesium, lithium, potassium,calcium, etc. are used to neutralize some portion of the acid groups inthe copolymer resulting in a thermoplastic elastomer exhibiting enhancedproperties, i.e. improved durability, etc. for golf ball constructionover balata.

Broadly, the ionic copolymers comprise one or more alpha-olefins andfrom about 9 to about 30 weight percent of alpha, beta-ethylenicallyunsaturated mono- or dicarboxylic acid, the basic copolymer neutralizedwith metal ions to the extent desired. Usually, at least 20% of thecarboxylic acid groups of the copolymer are neutralized by the metalions (such as sodium, potassium, manganese, zinc, lithium, calcium,nickel, magnesium, and the like) and exist in the ionic state. Ingeneral, ionic copolymers including up to 16% acid are considered "lowacid"ionomers, while those including greater than 16% acid areconsidered "high acid"ionomers by the present inventors.

Suitable olefins for use in preparing the ionomeric resins includeethylene, propylene, butene-1, hexene-1, and the like. Unsaturatedcarboxylic acids include acrylic, methacrylic, ethacrylic,α-chloroacrylic, crotonic, maleic, fumaric, itaconic acids, and thelike. The ionomeric resins utilized in the golf ball industry aregenerally copolymers of ethylene with acrylic (i.e. Escor®) and/ormethacrylic (i.e. Surlyn®) acid. In addition, two or more types ofionomeric resins may be blended into the cover compositions in order toproduce the desired properties of the resulting golf balls.

Along this line, the properties of the cover compositions and/or theionomeric resins utilized in the golf ball industry vary according tothe type and amount of the metal cation, the molecular weight, thecomposition of the base resin (i.e. the nature and the relative contentof the olefin, the unsaturated carboxylic acid groups, etc.), the amountof acid, the degree of neutralization and whether additional ingredientssuch as reinforcement agents or additives are utilized. Consequently,the properties of the ionomer resins can be controlled and varied inorder to produce golf balls having different playing characteristics,such as differences in hardness, playability (i.e. spin, feel, click,etc.), durability (i.e. impact and/or cut resistance), and resilience(i.e. coefficient of restitution).

However, while there are currently more than fifty commercial grades ofionomers available from DuPont and Exxon with a wide range of propertieswhich vary according to the type and amount of metal cations, molecularweight, composition of the base resin (i.e. relative content of ethyleneand methacrylic and/or acrylic acid groups), the degree ofneutralization and additive ingredients such as reinforcement agents,etc., a great deal of research continues in order to develop golf ballcover compositions exhibiting not only the playability characteristicspreviously associated with the balata cover, but also the improvedimpact resistance and carrying distance properties produced by theionomeric resins. Thus, an object of the present invention is to providegolf ball cover compositions which, when utilized in golf ballconstruction, produce balls exhibiting improved travel distance whilemaintaining satisfactory playability and durability properties such ascoefficient of restitution (C.O.R.).

A golf ball's coefficient of restitution (C.O.R.) is the ratio of therelative velocity of the ball after direct impact to that before impact.One way to measure the coefficient of restitution is to propel a ball ata given speed against a hard massive surface, and measure its incomingvelocity and outgoing velocity. The coefficient of restitution isdefined as the ratio of the outgoing velocity to incoming velocity of arebounding ball and is expressed as a decimal. As a result, thecoefficient of restitution can vary from zero to one, with one beingequivalent to an elastic collision and zero being equivalent to aninelastic collision.

The coefficient of restitution of a one-piece golf ball is a function ofthe ball's composition. In a two-piece or a multi-layered golf ball, thecoefficient of restitution is a function of the core, the cover and anyadditional layer. While there are no United States Golf Association(U.S.G.A.) limitations on the coefficient of restitution values of agolf ball, the U.S.G.A. requires that the golf ball cannot exceed aninitial velocity of 255 feet/second. As a result, golf ballmanufacturers generally seek to maximize the coefficient of restitutionof a ball without violating the velocity limitation.

In various attempts to produce a high coefficient of restitution golfball exhibiting the enhanced travel distance desired, the golfingindustry has blended various ionomeric resins. However, many of theseblends do not exhibit the durability and playability characteristicsnecessary for repetitive play and/or the enhanced travel distancedesired.

It is, therefore, desirable to develop golf ball cover compositionswhich produce golf balls exhibiting properties of desired carryingdistance (i.e., possess desirable coefficient of restitution values)over known ionomeric cover blends such as those set forth in U.S. Pat.Nos. 4,884,814 and 4,911,451, without sacrificing or improvingplayability and/or durability characteristics.

Furthermore, while as stated above, Surlyn® and Escor® (i.e. "Iotek")are materials of choice for golf ball cover construction when balata isnot used, these materials are relatively costly. It has, therefore,become desirable to develop a low cost alternative to Surlyn® and Iotek(Escor®) ionomeric resins in golf ball cover construction while at thesame time maintaining properties such as good coefficient of restitution(C.O.R.), softness, as well as the durability required for repetitiveplay.

These and other objects and features of the invention will be apparentfrom the following description and from the claims.

SUMMARY OF THE INVENTION

The present invention is directed to golf ball covers, and moreparticularly to golf ball cover compositions which comprise blends ofhigh or low acid copolymers with ethylene alkyl acrylates. The golf ballcovers of the invention provide a desirable low cost alternative to theSurlyn® and Iotek ionomeric resins so frequently used in golf ball coverconstruction when balata is not used.

The present invention is particularly directed to golf ball covercompositions which are prepared by blending an acid copolymer whichcontains about 1% to about 25% acrylic acid, such as an ethylene acrylicacid (EAA) copolymer, with an ethylene copolymer including up to about30% by weight of an alkyl acrylate. The alkyl acrylate in the ethylenecopolymer may be selected from among ethyl acrylate, methyl acrylate,butyl acrylate, or others. The ethylene copolymer may, therefore,comprise among others ethylene ethyl acrylate (EEA), ethylene methylacrylate (EMA), and/or ethylene butyl acrylate (EBA). The blending stepis followed by the addition of a cation or cation blend forneutralization.

The selection of type and ratio of the ethylene acrylic acid (EAA)copolymer to the ethylene alkyl acrylate (i.e., EEA, EBA, EMA, etc.) isbased on the desired final hardness and spin rate of the ball.Preferably, the blend of the acid copolymer with the non-acid functionalethylene alkyl acrylate includes about 30 to 90 parts by weight acidcopolymer, and about 10 to 70 parts by weight ethylene alkyl acrylate.More preferably, the blend is comprised of about 40 to 50 parts byweight acid copolymer and about 50 to 60 parts by weight ethylene alkylacrylate. Most preferably the blend consists of about 50 to about 70parts by weight acid copolymer and about 30 to 50 parts by weightethylene alkyl acrylate.

In another aspect, the invention relates to a metal cation neutralizedionomer resin comprising a blend of i) a copolymer of about 1 weightpercent to about 25 weight percent, preferably greater than 16 weightpercent of an alpha, beta-unsaturated carboxylic acid (preferablyacrylic acid) and an olefin (preferably ethylene), and ii) an ethylenealkyl acrylate. Approximately, 10% to about 90% of the carboxyl groupsof the acid copolymer are neutralized with a metal cation such as ametal cation selected from the group consisting of manganese, lithium,potassium, calcium, maganese, zinc, sodium, and nickel.

In a further aspect, the present invention concerns a metal cationneutralized high acid ionomer resin comprising a blend of i) a copolymerconsisting of about 17 to 25 percent by weight acrylic acid with theremainder, or balance, thereof being ethylene and ii) an ethylene alkylacrylate. Approximately, 10% to 90% of the carboxyl groups of the acidcopolymer are neutralized with a metal cation such as a metal cationselected from the group consisting of manganese, lithium, potassium,zinc, sodium, magnesium, calcium, and nickel.

In another further aspect, the invention relates to a golf ballcomprising a core and a cover, wherein the cover is comprised of a blendof i) a copolymer of about 20% by weight of an acrylic acid and theremainder ethylene and ii) an ethylene alkyl acrylate, of which 10% to90% of the carboxyl groups of the acrylic acid/ethylene copolymer areneutralized with a metal cation such as a metal cation selected from thegroup consisting of manganese, lithium, potassium, sodium, zinc,magnesium, calcium and nickel. In addition, the cover may contain one ormore additional ingredients such as pigments, dyes, U.V. absorbers andoptical brighteners. The core is generally a solid core.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the development of golf ball covers,and more particularly to golf ball cover compositions which compriseblends of ethylene copolymers (i.e., ethylene alkyl acrylates) with acidcopolymers. These blends may be reacted with a neutralizing compoundsuch as magnesium oxide, zinc oxide, zinc acetate, etc. In this regard,a golf ball cover having good durability, playability (spin) and C.O.R.at a low cost relative to Surlyn® or Iotek is provided.

The acid copolymer used herein may contain anywhere from 1 to 25 percentby weight and, it is preferable to utilize a high acid copolymer (i.e. acopolymer containing greater than 16% by weight acid, preferably fromabout 17 to about 25 weight percent acid, and more preferably about 20weight percent acid). The acid copolymer is blended with the ethylenealkyl acrylate and the blend is neutralized with a metal cation saltcapable of ionizing or neutralizing the copolymer to the extent desired(i.e. from about 10% to 90%).

The base acid copolymer is preferably made up of greater than 16% byweight of an alpha, beta-unsaturated carboxylic acid and analpha-olefin. Optionally, a softening comonomer can be included in thecopolymer. Generally, the alpha-olefin has from 2 to 10 carbon atoms andis preferably ethylene, and the unsaturated carboxylic acid is acarboxylic acid having from about 3 to 8 carbons. Examples of such acidsinclude acrylic acid, methacrylic acid, ethacrylic acid, chloroacrylicacid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, withacrylic acid being preferred.

The softening comonomer that can be optionally included in the inventionmay be selected from the group consisting of vinyl esters of aliphaticcarboxylic acids wherein the acids have 2 to 10 carbon atoms and vinylethers wherein the alkyl groups contain 1 to 10 carbon atoms.

Consequently, examples of a number of copolymers suitable for use in theinvention include, but are not limited to, high acid embodiments of anethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer,an ethylene/itaconic acid copolymer, an ethylene/maleic acid copolymer,an ethylene/methacrylic acid/vinyl acetate copolymer, anethylene/acrylic acid/vinyl alcohol copolymer, etc. The base copolymerbroadly contains greater than 16% by weight unsaturated carboxylic acid,from about 30 to about 83% by weight ethylene and from 0 to about 40% byweight of a softening comonomer. More preferably, the copolymer containsabout 20% by weight unsaturated carboxylic acid and about 80% by weightethylene. Most preferably, the copolymer contains about 20% acrylic acidwith the remainder being ethylene.

Along these lines, examples of the preferred high acid base copolymerswhich fulfill the criteria set forth above, are a series ofethylene-acrylic acid copolymers which are commercially available fromThe Dow Chemical Company, Midland, Mich., under the "Primacor"designation. These high acid base copolymers exhibit the typicalproperties set forth below in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Typical Properties of Primacor                                                Ethylene-Acrylic Acid Copolymers                                                               MELT TENSILE                                                                            FLEXURAL                                                                            VICAT                                             PERCENT                                                                             DENSITY,                                                                            INDEX,                                                                             YD. ST                                                                             MODULUS                                                                             SOFT PT                                                                            SHORE D                                 GRADE                                                                              ACID  glcc  g/10 min                                                                           (psi)                                                                              (psi) (° C.)                                                                      HARDNESS                                __________________________________________________________________________    ASTM       D-792 D-1238                                                                             D-638                                                                              D-790 D-1525                                                                             D-2240                                  5980 20.0  0.958  300.0                                                                             --   4800  43   50                                      5990 20.0  0.955 1300.0                                                                             650  2600  40   42                                      5990 20.0  0.955 1300.0                                                                             650  3200  40   42                                      5981 20.0  0.960  300.0                                                                             900  3200  46   48                                      5983 20.0  0.958  500.0                                                                             850  3100  44   45                                      5991 20.0  0.953 2600.0                                                                             635  2600  38   40                                      __________________________________________________________________________     .sup.1 The Melt Index values are obtained according to ASTM D1238, at         190° C.                                                           

Due to the high molecular weight of the Primacor 5981 grade of theethylene-acrylic acid copolymer, this copolymer is the more preferredgrade utilized in the invention.

Other acid copolymers which may be used include an ethylene-methacrylicacid copolymer such as Nucrel® available from E.I. DuPont de Nemours &Co. Nucrel® is an ethylene copolymer which is inherently flexible likeEVA copolymers, and which offers desirable performance characteristicssimilar to those of Surlyn® ionomers.

The Nucrel® acid copolymers are produced by reacting ethylene andmethacrylic acid in the presence of free radical initiators. A branched,random ethylene methacrylic acid (EMAA) copolymer is produced thereby.Carboxyl groups are distributed along the chain and interact withcarboxyl groups on adjacent molecules to form a weakly crosslinkednetwork through hydrogen bonding. The carboxyl groups disrupt thelinearity of the polyethylene.

Nucrel® acid copolymers offer tensile strength as high as 25 MPa (3,600psi) and good performance at low temperatures (945 k J/m² at -40° C.).Properties of selected Nucrel® acid copolymers are listed in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    TYPICAL PROPERTIES OF NUCREL ® ACID COPOLYMER RESINS                                        NUC- NUC-                                                                              NUC- NUC-                                                                              NUC- NUC-                                                                              NUC- NUC-                                                                              NUC- NUC-                                 REL ®                                                                          REL ®                                                                         REL ®                                                                          REL ®                                                                         REL ®                                                                          REL ®                                                                         REL ®                                                                          REL ®                                                                         REL ®                                                                          REL ®          PROPERTY                                                                             UNITS  ASTM                                                                              010  035 403  410 535  599 699  714 925  960                __________________________________________________________________________    Melt Index                                                                           dg/min D1238                                                                             11   35  3.0  10  35   500 88   14  21   60                 Density                                                                              g/cm.sup.3                                                                           D792                                                                              .934 0.94                                                                              .934 .933                                                                              .934 .918                                                                              .937 .937                                                                              0.97 .941               Tensile                                                                              MPa(kpsi)                                                                            D638                                                                              22.1 17.9                                                                              24.7 21.4                                                                              21.4 10.3                                                                              15.2 22.7                                                                              25   21.4               Strength          (3.2)                                                                              (2.6)                                                                             (3.6)                                                                              (3.1)                                                                             (3.1)                                                                              (1.5)                                                                             (2.2)                                                                              (3.3)                                                                             (3.6)                                                                              (3.1)              Elongation                                                                           %      D638                                                                              630  640 568  600 580  530 560  560 520  540                Flexural                                                                             MPa(kpsi)                                                                            D790                                                            Modulus                                                                       23° C.     40.0 59  152  93.8                                                                              71   64.8                                                                              68.3 66.9                                                                              74   55.1               (73° F.)   (5.8)                                                                              (8.6)                                                                             (22) (13.6)                                                                            (10.3)                                                                             (9.4)                                                                             (9.9)                                                                              (9.7)                                                                             (10.8)                                                                             (8.0)              Hardness                                                                             Shore D                                                                              D2240                                                                             40   40  53   49  48   42  46   50  50   46                 Vicat  ° C.                                                                          D1525,                                                                            64   60  83   80  75   65  71   74  67   62                 Softening                                                                            (° F.)                                                                        Rate B                                                                            (147)                                                                              (140)                                                                             (181)                                                                              (176)                                                                             (167)                                                                              (149)                                                                             (160)                                                                              (165)                                                                             (153)                                                                              (144)              Temperature                                                                   Notched Izod                                                                         J/m (ft-lb/in)                                                                       256 NB.sup.1                                                                           374 (7)                                                                           NB   NB  NB   NB  NB   NB  801  NB                                                                       (15)                    Tensile                                                                              kJ/m.sup.2 (ft-lb/in.sup.2)                                                          1822S                                                           Impact                                                                        23° C.     998  1,060                                                                             756  872 723  413 491  812 755  606                2(73° F.)  (475)                                                                              (505)                                                                             (360)                                                                              (415)                                                                             (344)                                                                              (196)                                                                             (233)                                                                              (386)                                                                             (360)                                                                              (289)              -40° C.    647  945 442  707 486  55  288  465 275  342                (-40° F.)  (308)                                                                              (450)                                                                             (210)                                                                              (336)                                                                             (231)                                                                              (26)                                                                              (137)                                                                              (221)                                                                             (130)                                                                              (163)              __________________________________________________________________________     NB = Na Break                                                            

The cover may comprise about 30-90 percent by weight of an acidcopolymer, preferably about 40-80 percent, and most preferably 50-70percent acid copolymers. At the same time, the cover may comprise about10-70 percent by weight of an ethylene copolymer, preferably 20-60percent, and most preferably 30-50 percent ethylene copolymer.

Ethylene copolymers which may be used herein include ethylene-ethylacrylate (EEA) , ethylene-methyl acrylate (EMA), and ethylene-butylacrylate copolymers. Ethylene-ethyl acrylate is made by thepolymerization of ethylene units with randomly distributed ethyleneacrylate (EA) comonomer groups. The ethylene-ethyl acrylate copolymerscontain up to about 30% by weight of ethylene acrylate. They are tough,flexible products having a relatively high molecular weight. They havegood flexural fatigue and low temperature properties (down to -65° C) .In addition, EEA resists environmental stress cracking as well asultraviolet radiation.

Examples of ethylene-ethyl acrylate which may be used herein includeBakelite® DPD-6169 or Bakelite® DPD-6182 available from Union Carbide.Properties of these and other suitable ethylene-ethyl acrylatecopolymers include:

                  TABLE 3                                                         ______________________________________                                        TYPICAL PROPERTIES OF UNION CARBIDE                                           ETHYLENE-ETHYL ACRYLATE                                                                         TEST     DPD-   DPD-  DPD-                                  PROPERTY          METHOD   6169   6182  9169                                  ______________________________________                                        Melt Index, g/10 minutes                                                                        D 1239   6      1.5   20                                    Density, g/cm.sup.3                                                                             D 1505   0.931  0.930 0.931                                 Flexural Modulus, psi.sup.(a)                                                                   D 790    9,500  13,000                                                                              9,000                                 Secant Modulus of Elasticity, psi.sup.(a)                                                       D 639    5,000  6,200 4,300                                 Ultimate Elongation, %.sup.(a)                                                                  D 639    700    700   750                                   Tensile Strength, psi.sup.(a)                                                                   D 638    1,600  2,100 700                                   Yield Strength, psi.sup.(b)                                                                     D 638    550    700                                         Bent Strip Stress Cracking                                                                      D 1693   >500   <1,000                                                                              350                                   Resistance, 100% "Igepal" Solvent,                                            F.sub.50, hours                                                               Durometer Hardness,                                                                             D 676                                                       "A"                        88     87    86                                    "D"                        32     32    31                                    Brittleness Index, 50% Failure, ° C.                                                     D 746    -105   66                                          Vicat Softening Point, ° C.                                                              D 1525   64                                                 Compression Set, 10 days at 23° C.,                                                      D 395    56                                                 % recovery                                                                    ______________________________________                                         .sup.(a) Determined on 0.075 inch compression molded plagues.                 .sup.(b) Determined on 0.075 inch compression molded plagues. Material ha     no true yield point. Value represents tens tensile strength at 50%            elongation.                                                              

EEA is similar to ethylene vinyl acetate (EVA) in its density-propertyrelationships and high-temperature resistance. In addition, like EVA,EEA is not resistant to aliphatic and aromatic hydrocarbons. Forcomparison purposes, some typical properties of ionomers as well asethylene vinyl acetate and ethylene ethyl acrylate are provided below:

                  TABLE 4                                                         ______________________________________                                        TYPICAL PROPERTIES OF IONOMERS AND EEA                                                       Ionomer EVA       EEA  UNITS                                   ______________________________________                                        Specific gravity                                                                             0.93    0.93-0.95 0.93                                         Yield strength 2.2     1.3       1.05 10.sup.3 lbf/in.sup.2                   Tensil modules 28-40   11        6    10.sup.3 lbf/in.sup.2                   Usual form of fracture                                                                       tough   tough     tough                                        Vicat softening point                                                                        71      83        64   ° C.                             ASTM brittleness temperature                                                                 -100    -70       -100 ° C.                             Power Factor 10.sup.2 Hz                                                                     0.0015  0.0024    0.001                                        Dielectric constant 10.sup.3 Hz                                                              2.5     2.8       2.8                                          ______________________________________                                    

Ethylene-methyl acrylate copolymers contain up to about 30% by weight ofmethyl acrylate and yield blown films having rubberlike limpness andhigh impact strength. These copolymers may be useful in coating andlaminating applications as a result of their good adhesion to commonlyused substrates. EMAs have good heat-seal characteristics.

Ethylene-methyl acrylate copolymers are manufactured by reacting, athigh temperatures and pressures, methyl-acrylate monomers with ethyleneand free radical initiators. Polymerization occurs such that the methylacrylate forms random side chains on the polyethylene backbone. Theacrylic functionality decreases resin crystallinity and increasespolarity to enhance resin properties. The properties depend on molecularweight (determined by melt index) and percent crystallinity. Percentcrystallinity is determined by comonomer incorporation. As the comonomercontent increases, the film become softer, tougher, and easier to heatseal.

EMA films have low modulus (<10,000 psi), low melting points, and goodimpact strength. In addition, the EMA resins are highly polar, and as aresult are compatible with olefinic and other polymers. They adhere wellto many substrates including LDPE, LLDPE, and EVA.

Examples of ethylene-methyl acrylate which may be used in the golf ballcover compositions of the present invention include the Optema™ orEscor® EMA copolymer resins available from Exxon Chemical Company. TheOptema™/Escor® EMA resins are thermally stable ethylene methyl acrylateresins which will accept up to 65% or more fillers and pigments withoutlosing their properties. They are more thermally stable than EVAs andcan be extruded or molded over a range of 275-625° F. (compared to anEVA limit of 450° F.). EMAs are generally not corrosive when compared toEVAs, EAAs and ionomers. Some of the typical properties associated withthe various grades of Optema™ EMA resins are found in the followingTable 5:

                                      TABLE 5                                     __________________________________________________________________________    PROPERTIES OF OPTEMA ™ EMA RESINS                                                                                                  VICAT                      MELT           TENSILE                                                                             FLEXURAL    HARDNESS                                                                            TENSILE     SOFTENING                  INDEX     DENSITY                                                                            STRENGTH                                                                            MODULUS     SHORE IMPACT @                                                                             ELON-                                                                              PT                         dg/min                                                                            METHYL                                                                              g/cm.sup.3                                                                         psi (MPa)                                                                           psi (MPa)                                                                           MELTING                                                                             A/D   73° F. (23°                                                            GATION                                                                             (10,000)              OPTEMA                                                                             (ASTM                                                                             ACRYLATE                                                                            (ASTM                                                                              (ASTM (ASTM POINT (ASTM (ASTM  % (ASTM                                                                            (ASTM                 GRADE                                                                              D1238)                                                                            WT %  D1505)                                                                             D638) D790) ° F. (° C.)                                                           D2240)                                                                              D1822) D638)                                                                              D1525)                __________________________________________________________________________    TC 020                                                                             6.0 6.5   0.928                                                                              1700 (12)                                                                           17500 215 (102)                                                                           >90/45                                                                              170 (360)                                                                            >800 172 (78)                                        (120)                                               TC 115                                                                             0.7 16.5  0.938                                                                              1900 (13)                                                                           8300 (57)                                                                           185 (85)                                                                            91/41 260 (550)                                                                            >800 149 (65)              TC 114                                                                             3.2 18.0  0.948                                                                              1700 (12)                                                                           7100 (49)                                                                           178 (81)                                                                            89/38 260 (570)                                                                            >800 133 (56)              TC 110                                                                             2.0 21.5  0.942                                                                              1600 (11)                                                                           5100 (35)                                                                           167 (75)                                                                            86/36 270 (570)                                                                            >800 126 (52)              TC 111                                                                             2.0 21.5  0.944                                                                              1600 (11)                                                                           5100 (35)                                                                           167 (75)                                                                            86/36 270 (570)                                                                            >800 126 (52)              TC 420                                                                             6.0 20.   0.942                                                                              1600 (11)                                                                           5100 (35)                                                                           169 (76)                                                                            86/35 250 (520)                                                                            >800 117 (47)              TC 130                                                                             20.0                                                                              21.5  0.941                                                                              1300 (9)                                                                            4900 (34)                                                                           167 (75)                                                                            85/33 230 (480)                                                                            >800 109 (43)              TC 140                                                                             135.0                                                                             21.5  0.939                                                                              1200 (8)                                                                            4900 (34)                                                                           162 (72)                                                                            84/32 170 (360)                                                                            >800 97 (36)               TC 113                                                                             1.0 23.5  0.939                                                                              1600 (11)                                                                           3700 (26)                                                                           165 (74)                                                                            83/33 310 (650)                                                                            >800 127 (50)              TC 220                                                                             5.0 24.0  0.945                                                                              1300 (9)                                                                            3900 (27)                                                                           156 (69)                                                                            82/32 280 (580)                                                                            >800 109 (43)              TC 221                                                                             5.0 27.0  0.948                                                                              1100 (8)                                                                            2800 (19)                                                                           147 (64)                                                                            79/28 280 (590)                                                                            >800 102 (39)              DEVEL-                                                                        OP-                                                                           MENTAL                                                                        GRADES                                                                        XS-11.04                                                                           6.0 6.0   0.933                                                                              1410  11,4000                                                                             225 (107)                                                                           90/35 170 (363)                                                                            1450 182 (84)                                  (13.3)                                                                              (78.6)                                              XS-12.04                                                                           3.0 28.0  0.953                                                                              760 (5.0)                                                                           1210 (8.3)                                                                          145 (63)                                                                            70/17 --     1060 --                    XS-13.04                                                                           135.0                                                                             20.   0.940                                                                              700 (4.8)                                                                           2800 (19)                                                                           171 (77)                                                                            82/25 --     1400 121                   __________________________________________________________________________                                                            (50)              

Certain developmental grades of Optema™ EMAs may be used in formulatingthe golf ball covers herein. These developmental grades of resins aredesignated "XS". Pertinent properties of XS-11.04, 12.04 and 13.04 areset forth above in Table 5. Melt index and methyl acrylate content ofthese and certain others are set forth in the following Table 6:

                  TABLE 6                                                         ______________________________________                                        PROPERTIES OF OPTEMA ® DEVELOPMENTAL EMA RESINS                                      MELT INDEX     METHYLACRYLATE                                      OPTIMER/GRADE                                                                             (dg/min)      CONTENT (%)                                         ______________________________________                                        XS-53.04   0.7            15                                                  XS-54.04   1.0            24                                                  XS-34.14*  2.0            20                                                  XS-12.04   3.0            28                                                  XS-61.48   5.0            24                                                  XS-55.48   5.0            28                                                  XS-11.04   6.0             6                                                  XS-13.04   135.0          20                                                  ______________________________________                                         *Slip and antiblock added.                                               

Chevron Chemical Company's ethylene-butyl acrylate copolymer, EBAC™, isstable at high temperatures, and may be processed as high as 600° F.Typical properties (or average values) of certain EBAC™ copolymers areset forth below in Table 7.

                                      TABLE 7                                     __________________________________________________________________________    PROPERTIES OF ETHYLENE-BUTYL ACRYLATE COPOLYMERS (EBAC ™ )                                 EBAC ™                                                                          EBAC ™                                                                DS-  DS-  EBAC ™                                                                          EBAC ™                                                                          EBAC ™                                                 1263-                                                                              1120-                                                                              DS-  DS-  DS-                                       PROPERTIES                                                                           UNITS                                                                             ASTM 70   70   1122-70                                                                            1123-70                                                                            1256-70                                   __________________________________________________________________________    Melt Flow                                                                            gms/10                                                                            D-1238                                                                             0.5  2.0  6.0  20   3.0                                              min                                                                    Butyl  %   --   18   20   20   20   28.0                                      Acrylate                                                                      Content                                                                       Density                                                                              gm/cc                                                                             D-1505                                                                             0.927                                                                              0.927                                                                              0.927                                                                              0.927                                                                              0.927                                     Melting                                                                              ° C.                                                                       --   91   90   87   88   74                                        Point                                                                         Vicat  ° C.                                                                       D-1525                                                                             65   60   55   49                                             Softening                                                                     Point                                                                         Brittleness                                                                          ° C.                                                                       D-746                                                                              <-76 <-75 <-75 <-75 <-76                                      Temperature                                                                   Hardness                                                                      Shore A                                                                              --  D-2240                                                                             --   --   88   88   74                                        Shore D                                                                              --  D-2240                                                                             38   33   --   27   23                                        Flexural                                                                             psi D-747                                                                              4000 --   --   3000                                           Stiffness                                                                     Tensile                                                                              psi D-638                                                                              2000 1400 1100 680  760                                       Ultimate.sup.2                                                                Tensile @                                                                            psi D-638                                                                              1900 1400 1100 680  760                                       Break.sup.2                                                                   Elongation                                                                           %   D-638                                                                              810  900  850  620  950                                       @ point                                                                       Break.sup.2                                                                   __________________________________________________________________________     .sup.1 Melt Flow testing of condition E, 190° C. and 2.16 kg           weight.                                                                       .sup.2 Tensile Properties determined with Type IV compression molded          samples, 20°/min crosshead speed.                                 

The metal cation salts utilized in the invention are those salts whichprovide the metal cations capable of neutralizing, to various extents,the carboxylic acid groups of the high acid copolymer. These includeacetate, oxide or hydroxide salts of lithium, calcium, zinc, sodium,potassium, nickel, magnesium, and manganese.

Examples of such lithium ion sources are lithium hydroxide monohydrate,lithium hydroxide, lithium oxide and lithium acetate. Sources for thecalcium ion include calcium hydroxide, calcium acetate and calciumoxide. Suitable zinc ion sources are zinc acetate dihydrate and zincacetate, a blend of zinc oxide and acetic acid. Examples of sodium ionsources are sodium hydroxide and sodium acetate. Sources for thepotassium ion include potassium hydroxide and potassium acetate.Suitable nickel ion sources are nickel acetate, nickel oxide and nickelhydroxide. Sources of magnesium include magnesium oxide, magnesiumhydroxide, magnesium acetate. Sources of manganese include manganeseacetate and manganese oxide.

The cover compositions of the invention are produced by reacting theblend of the acid copolymer and the ethylene alkyl acrylate with variousamounts of the metal cation salts above the crystalline melting point ofthe copolymer, such as at a temperature from about 200° F. to about 500°F., preferably from about 250° F. to about 350° F. under high shearconditions at a pressure of from about 100 psi to 10,000 psi. Other wellknown blending techniques may also be used. The amount of metal cationsalt utilized to produce the cover compositions is the quantity whichprovides a sufficient amount of the metal cations to neutralize thedesired percentage of the carboxylic acid groups in the high acidcopolymer. The extent of neutralization is generally from about 10% toabout 90%.

Additional compatible additive materials may also be added to thecompositions of the present invention, such as dyes (for example,Ultramarine Blue sold by Whitaker, Clark, and Daniels of SouthPainsfield, N.J.), and pigments, i.e. white pigments such as titaniumdioxide (for example Unitane 0-110) zinc oxide, and zinc sulfate, aswell as fluorescent pigments. As indicated in U.S. Pat. No. 4,884,814,the amount of pigment and/or dye used in conjunction with the polymericcover composition depends on the particular base ionomer mixtureutilized and the particular pigment and/or dye utilized. Theconcentration of the pigment in the polymeric cover composition can befrom about 1% to about 10% as based on the weight of the base ionomermixture. A more preferred range is from about 1% to about 5% as based onthe weight of the base ionomer mixture. The most preferred range is fromabout 1% to about 3% as based on the weight of the base ionomer mixture.The most preferred pigment for use in accordance with this invention istitanium dioxide.

Moreover, since these are various hues of white, i.e. blue white, yellowwhite, etc., trace amounts of blue pigment may be added to the coverstock composition to impart a blue white appearance thereto. However, ifdifferent hues of the color white are desired, different pigments can beadded to the cover composition at the amounts necessary to produce thecolor desired.

In addition, it is within the purview of this invention to add to thecover compositions of this invention compatible materials which do notaffect the basic novel characteristics of the composition of thisinvention. Among such materials are antioxidants (i.e. Santonox R) ,antistatic agents, stabilizers and processing aids. The covercompositions of the present invention may also contain softening agents,such as plasticizers, etc., and reinforcing materials such as glassfibers and inorganic fillers, as long as the desired properties producedby the golf ball covers of the invention are not impaired.

Furthermore, optical brighteners, such as those disclosed in U.S. Pat.No. 4,679,795, may also be included in the cover composition of theinvention. Examples of suitable optical brighteners which can be used inaccordance with this invention are Unitex OB as sold by the Ciba-GeigyChemical Company, Ardaley, N.Y. Unitex OB is thought to be 2, 5-Bis(5-tert-butyl-2-benzoxazoly) thiophene. Examples of other opticalbrighteners suitable for use in accordance with this invention are asfollows: Leucopure EGM as sold by Sandoz, East Hanover, N.J. 07936.Leucopure EGM is thought to be 7-(2h-naphthol (1,2-d)-triazol-2yl)-3phenyl-coumarin. Phorwhite K-20G2 is sold by Mobay ChemicalCorporation, P.O. Box 385, Union Metro Park, Union, N.J. 07083, and isthought to be a pyrazoline derivative, Eastobrite OB-1 as sold byEastman Chemical Products, Inc. Kingsport, Tenn., is thought to be4,4-Bis (-benzoxaczoly) stilbene. The above-mentioned Uvitex andEastobrite OB-1 are preferred optical brighteners for use in accordancewith this invention.

Moreover, since many optical brighteners are colored, the percentage ofoptical brighteners utilized must not be excessive in order to preventthe optical brightener from functioning as a pigment or dye in its ownright.

The percentage of optical brighteners which can be used in accordancewith this invention is from about 0.01% to about 0.5% as based on theweight of the polymer used as a cover stock. A more preferred range isfrom about 0.05% to about 0.25% with the most preferred range from about0.10% to about 0.020% depending on the optical properties of theparticular optical brightener used and the polymeric environment inwhich it is a part.

Generally, the additives are admixed with a ionomer to be used in thecover composition to provide a masterbatch (M.B.) of desiredconcentration and an amount of the masterbatch sufficient to provide thedesired amounts of additive is then admixed with the copolymer blends.

The cover compositions of the present invention may be producedaccording to conventional melt blending procedures. In this regard, theabove indicated high acid ionomeric resins are blended along with themasterbatch containing the desired additives in a Banbury type mixer,two-roll mill, or extruded prior to molding. The blended composition isthen formed into slabs or pellets, etc. and maintained in such a stateuntil molding is desired. Alternatively a simple dry blend of thepelletized or granulated resins and color masterbatch may be preparedand fed directly into the injection molding machine where homogenizationoccurs in the mixing section of the barrel prior to injection into themold. If necessary, further additives such as an inorganic filler, etc.,may be added and uniformly mixed before initiation of the moldingprocess.

Moreover, golf balls of the present invention can be produced by moldingprocesses currently well known in the golf ball art. Specifically, thegolf balls can be produced by injection molding or compression moldingthe novel cover compositions about wound or solid molded cores toproduce a golf ball having a diameter of about 1.680 inches or greaterand weighing about 1.620 ounces. The standards for both the diameter andweight of the balls are established by the United States GolfAssociation (U.S.G.A.). Although both solid core and wound cores can beutilized in the present invention, as a result of their lower cost andsuperior performance, solid molded cores are preferred over wound cores.

Conventional solid cores are typically compression molded from a slug ofuncured or lightly cured elastomer composition comprising a high ciscontent polybutadiene and a metal salt of an α, β, ethylenicallyunsaturated carboxylic acid such as zinc mono or diacrylate ormethacrylate. To achieve higher coefficients of restitution in the core,the manufacturer may include a small amount of a metal oxide such aszinc oxide. In addition, larger amounts of metal oxide than those thatare needed to achieve the desired coefficient may be included in orderto increase the core weight so that the finished ball more closelyapproaches the U.S.G.A. upper weight limit of 1.620 ounces. Othermaterials may be used in the core composition including compatiblerubbers or ionomers, and low molecular weight fatty acids such asstearic acid. Free radical initiator catalysts such as peroxides areadmixed with the core composition so that on the application of heat andpressure, a complex curing or cross-linking reaction takes place.

The term "solid cores" as used herein refers not only to one piece coresbut also to those cores having a separate solid layer beneath the coverand above the core as in U.S. Pat. No. 4,431,193, and other multilayerand/or non-wound cores (such as those described in U.S. Pat. No.4,848,770).

Wound cores are generally produced by winding a very large elasticthread around a solid or liquid filled balloon center. The elasticthread is wound around the center to produce a finished core of about1.4 to 1.6 inches in diameter, generally. Since the core material is notan integral part of the present invention, a detailed discussionconcerning the specific types of core materials which may be utilizedwith the cover compositions of the invention are not specifically setforth herein. In this regard, the cover compositions of the inventionmay be used in conjunction with any standard golf ball core.

As indicated, the golf balls of the present invention may be produced byforming covers consisting of the compositions of the invention aroundcores by conventional molding processes. For example, in compressionmolding, the cover composition is formed via injection at about 380° F.to about 450° F. into smooth surfaced hemispherical shells which arethen positioned around the core in a dimpled golf ball mold andsubjected to compression molding at 200-300° F. for 2-10 minutes,followed by cooling at 50-70° F. for 2-10 minutes, to fuse the shellstogether to form an unitary ball. In addition, the golf balls may beproduced by injection molding, wherein the cover composition is injecteddirectly around the core placed in the center of a golf ball mold for aperiod of time at a mold temperature of from 50° F. to about 100° F.After molding the golf balls produced may undergo various furtherfinishing steps such as buffing, painting, and marking as disclosed inU.S. Pat. No. 4,911,451.

The present invention is further illustrated by the following examplesin which the parts of the specific ingredients are by weight (pbw). Itis to be understood that the present invention is not limited to theexamples, and various changes and modifications may be made in theinvention without departing from the spirit and scope thereof.

EXAMPLES

By blending the ingredients set forth in the Tables below, a series ofgolf ball cover formulations were produced. Finished golf balls wereprepared using the cover compositions of the present invention, controlsand comparative cover compositions by positioning a solid preformedcross-linked polybutadiene core in an injection molding cavity in such amanner to permit the uniform injection of the selected cover compositionover each core. Along this line, the cover formulations were injectionmolded at about 400° F. around identical solid type cores having afinished diameter of 1.545 inches to produce golf balls approximately1.680 inches in diameter having a normal cover thickness of 0.0675inches. All materials were molded under essentially identicalconditions. The properties of coefficient of restitution (C.O.R.) of themolded and finished balls, Shore D hardness, cold crack resistance, spinrates, etc. for the cover compositions were then determined.

In conducting the comparative prior art testing, Escor® 4000/7030 andEscor® 900/8000 ionomers were utilized. In this regard, blends of Escor®4000/7030 and Escor® 900/8000 (i.e. the subject of U.S. Pat. No.4,911,451) are considered by the inventors to be generally among thebest prior art cover compositions concerning ethylene-acrylic acidionomer (low acid) blends.

The data for each example represents the average data for one dozenballs produced according to the desired manner. The properties for theExamples were measured according to the following parameters:

Coefficient of restitution (C.O.R.) was measured by firing the resultinggolf ball in an air cannon at a velocity of 125 feet per second againsta steel plate which is positioned 12 feet from the muzzle of the cannon.The rebound velocity was then measured. The rebound velocity was dividedby the forward velocity to give the coefficient of restitution.

Shore hardness was measured in accordance with ASTM Test D-2240.

Cold cracking resistance was measured by firing balls from an aircannon, 5 blows at 165 feet/sec, after the balls had been conditionedfor 24 hours at -10° F. After allowing the balls to equilibrate to roomtemperature the balls are inspected for cover cracking.

The spin rate of the golf ball was measured by striking the resultinggolf balls with a pitching wedge or 9-iron wherein the club-head speedis about 80 feet per second and the ball is launched at an angle of 26to 34 degrees with an initial velocity of about 110-115 feet per second.The spin rate was measured by observing the rotation of the ball inflight using stop action Strobe photography.

Example 1 Preparation of Acrylic Acid Based High Acid Ionomers

A number of new cation neutralized acrylic acid based high acid ionomerresins were prepared utilizing as the copolymer of an olefin and analpha, beta-unsaturated carboxylic acid, a 20 weight percent acrylicacid/ethylene copolymer produced by The Dow Chemical Company, Midland,Mich. under the designation "Primacor 5981." According to The DowChemical Company, Primacor 5981 has a melt index (at 190° C., 2150 g) of300 g/10 min. The carboxylic acid groups present in the 20 weightpercent acrylic acid/ethylene copolymer were neutralized to variousweight percentages by a number of different metal cation salts resultingin the production of several new thermoplastic elastomers exhibitingenhanced properties for golf ball cover production. Due to differencesin the nature of the cation salts, the amount of cation salts utilized,etc., the new high acid ionomer resins produced differed substantiallyin the extent of neutralization and in melt indices, as well as inresilience (i.e. C.O.R.) and hardness values.

For the purpose of determining the weight percent of neutralization ofthe carboxylic acid groups in the acrylic acid/ethylene copolymer afterreacting with various cation salts, it was assumed that 1 mole of sodium(Na⁺), potassium (K⁺), and lithium (Li⁺) neutralized one mole of acrylicacid, and that one mole of zinc (Zn²⁺), magnesium (Mg²⁺), manganese(Mn²⁺), calcium (Ca²⁺) and nickel (Ni²⁺) neutralized two moles ofacrylic acid. The calculations of neutralization were based upon anacrylic acid molecular weight of 79 g/m, giving 0.2778 moles per 100grams of copolymer.

As indicated below in Table 8, the various cation salts were added invariable amounts to the 20 weight percent acrylic acid/ethylenecopolymer in order to determine the optimal level of neutralization foreach of the cations. In Table 8, NaOH refers to sodium hydroxide(formula weight of 40). MnAc refers to manganese acetate tetrahydratehaving a formula weight of 245. LiOH is lithium hydroxide, fwt=24. KOHis potassium hydroxide, fwt=56. ZnAc is zinc acetate dihydrate,fwt=219.5. MgAc is magnesium acetate tetrahydrate, fwt=214.4. CaAc iscalcium acetate, fwt=158. MgO is magnesium oxide, fwt=40.3. NiAc isnickel acetate, fwt=176.8. All of these cation salts are solids at roomtemperature.

The specific cation salts were added in differing amounts with the 20weight percent acrylic acid/ethylene copolymer (i.e. the Primacor 5981)to an internal mixer (Banbury type) for the neutralization reaction. Theonly exception was calcium acetate, which, due to problems encounteredin solid form, was added as a 30 wt-% solution in water.

In the neutralization reaction, the cation salts solubilized in thePrimacor 5981 acrylic acid/ethylene copolymer above the melting point ofthe copolymer and a vigorous reaction took place with a great deal offoaming occurring as the cation reacted with the carboxylic acid groupsof the acrylic acid/ethylene copolymer and the volatile by-products ofwater (in the case of oxides or hydroxides) or acetic acid (whenacetates are used) were evaporated. The reaction was continued untilfoaming ceased (i.e. about 30-45 minutes at 250-350° F.), and the batchwas removed from the Banbury mixer. Mixing continued of the batchobtained from the mixer on a hot two-roll mill (175-250° F.) to completethe neutralization reaction. The extent of the reaction was monitored bymeasuring melt flow index according to ASTM D-1238-E. As indicatedbelow, the neutralized products exhibited drastically differentproperties depending upon the nature and amount of the cation saltsutilized.

                  TABLE 8                                                         ______________________________________                                        Formulation                                                                           Wt-%      Wt-%       Melt       Shore D                               No.     Cation Salt                                                                             Neutralization                                                                           Index                                                                              C.O.R.                                                                              Hardness                              ______________________________________                                        1(NaOH) 6.98      67.5       0.9  .804  71                                    2(NaOH) 5.66      54.0       2.4  .808  73                                    3(NaOH) 3.84      35.9       12.2 .812  69                                    4(NaOH) 2.91      27.0       17.5 .812  (brittle)                             5(MnAc) 19.6      71.7       7.5  .809  73                                    6(MnAc) 23.1      88.3       3.5  .814  77                                    7(MnAc) 15.3      53.0       7.5  .810  72                                    8(MnAc) 26.5      106        0.7  .813  (brittle)                             9(LiOH) 4.54      71.3       0.6  .810  74                                    10(LiOH)                                                                              3.38      52.5       4.2  .818  72                                    11(LiOH)                                                                              2.34      35.9       18.6 .815  72                                    12(KOH) 5.30      36.0       19.3 Broke 70                                    13(KOH) 8.26      57.9       7.18 .804  70                                    14(KOH) 10.7      77.0       4.3  .801  67                                    15(ZnAc)                                                                              17.9      71.5       0.2  .806  71                                    16(ZnAc)                                                                              13.9      53.0       0.9  .797  69                                    17(ZnAc)                                                                              9.91      36.1       3.4  .793  67                                    18(MgAc)                                                                              17.4      70.7       2.8  .814  74                                    19(MgAc)                                                                              20.6      87.1       1.5  .815  76                                    20(MgAc)                                                                              13.8      53.8       4.1  .814  74                                    21(CaAc)                                                                              13.2      69.2       1.1  .813  74                                    22(CaAc)                                                                              7.12      34.9       10.1 .808  70                                    ______________________________________                                        Controls:                                                                            50/50 Blend of Ioteks 8000/7030 C.O.R. = 810/65                               Shore D Hardness                                                              DuPont High Acid Surlyn ® 8422 (Na) C.O.R. = .811/70                      Shore D Hardness                                                              DuPont High Acid Surlyn ® 8162 (Zn) C.O.R. = .807/65                      Shore D Hardness                                                              Exxon High Acid Iotek Ex-960 (Zn) C.O.R. = .796/65                            Shore D Hardness                                                       ______________________________________                                                  Wt-%      Wt-%       Melt                                           Formulation No.                                                                         Cation Salt                                                                             Neutralization                                                                           Index  C.O.R.                                  ______________________________________                                        23(MgO)   2.91      53.5       2.5    .813                                    24(MgO)   3.85      71.5       2.8    .808                                    25(MgO)   4.76      89.3       1.1    .809                                    26(MgO)   1.96      35.7       7.5    .815                                    ______________________________________                                        Control for Formulations 23-26 15 50/50 Iotek 8000/7030,                      C.O.R. = .814, Formulation 26 C.O.R. was                                      normalized to that control accordingly                                        ______________________________________                                        Formulation                                                                           Wt-%      Wt-%       Melt       Shore D                               No.     Cation Salt                                                                             Neutralization                                                                           Index                                                                              C.O.R.                                                                              Hardness                              ______________________________________                                        27(NiAc)                                                                              13.04     61.1       0.2  .802  71                                    28(NiAc)                                                                              10.71     48.9       0.5  .799  72                                    29(NiAc)                                                                               8.26     36.7       1.8  .796  69                                    30(NiAc)                                                                               5.66     24.4       7.5  .786  64                                    ______________________________________                                        Control for Formulation Nos. 27-30 15 50/50                                   Iotek 8000/7030, C.O.R. = .807                                                ______________________________________                                    

As indicated in Table 8, a number of the new cation neutralized acrylicacid based high acid ionomer resins exhibited C.O.R. and Shore Dhardness values greater than that exhibited by a 50/50 blend of theIotek low acid acrylic acid based hard ionomer resins, such as the Iotek8000/7030 blend utilized in the cover compositions disclosed in U.S.Pat. No. 4,911,451. Moreover, included in new acrylic acid based highacid ionomer resins were numerous cation neutralized high acid ionomerresins previously not available, such as those acrylic acid based highacid ionomer resins neutralized to various degrees by the manganese,lithium, potassium, magnesium, calcium and nickel salts. Furthermore,the new cation neutralized acrylic acid based high acid ionomersproduced C.O.R. and hardness values greater than those shown by themethacrylic acid based high acid ionomer resins recently produced byDuPont (i.e. Surlyn® 8422 (Na) and Surlyn® 8162 (Zn)) and the acrylicacid based high acid resins experimentally produced by Exxon (i.e. IotekEX-959 and Ex-960 (Zn)), collectively referred to as "the controls."

In addition, the results produced by Formulation Nos. 1 through 3directed to the sodium ion neutralized ethylene-acrylic acid copolymersand Formulation Nos. 15 through 17 directed to the zinc ion neutralizedethylene-acrylic acid copolymers in comparison to the new Iotek highacid ethylene acrylic acid ionomers were also of interest. As indicatedabove, Escor® or Iotek Ex-959 is a sodium ion neutralizedethylene-acrylic acid copolymer and Escor® or Iotek Ex-960 is a zincneutralized ethylene-acrylic acid copolymer. According to Exxon, Ioteks959 and 960 contain from about 19.0 to about 21.0% by weight acrylicacid with approximately 30 to about 70 percent of the acid groupsneutralized with sodium and zinc ions, respectfully.

Formulation No. 2 (i.e. 5.66 wt-% sodium salt, 54 wt-% neutralization,2.4 melt index, 0.808 C.O.R. and 73 Shore D hardness) is somewhatsimilar to Iotek 959 and Formulation No. 16 (i.e. 13.9 wt-% zinc salt,53 wt-% neutralization, 0.9 melt index, 0.797 C.O.R. and 69 Shore Dhardness) is somewhat similar to Iotek 960.

However, not only did the new cation neutralized acrylic acid based highacid ionomers exhibit similar or better resilience (C.O.R.) atcomparable or better hardness values than those exhibited by the sodiumor zinc high acid Iotek ionomers, as a result of the neutralization ofthe acrylic acid/ethylene copolymer with several different cation salts,to a number of different neutralization percentages, a wide variety ofnew cation neutralized acrylic acid based high acid ionomers wereproduced having improved resilience and hardness values. These newcation neutralized high acid ionomer resins are particularly valuable inthe field of golf ball production.

More particularly, the development of a number of separate differentcation neutralized high acid ionomers besides the sodium or zinc highacid ionomers available from DuPont or Exxon, such as the new manganese,lithium, potassium, magnesium, calcium and nickel acrylic acid basedhigh acid ionomer resins, allows for the production of a wide variety ofcation neutralized high acid ionomer blends. Furthermore, since the newsodium or zinc neutralized high acid ionomers produced improvedproperties over those produced by the existing available sodium or zinchigh acid ionomers, a number of new cover compositions can be producedhaving enhanced characteristics.

Along this line, several of the cation neutralized acrylic acid basedhigh acid ionomer resins produced above which exhibited enhanced C.O.R.and Shore D hardness values were blended together and evaluated for thepurpose of determining whether any synergistic effects were producedparticularly with respect to enhanced C.O.R. values.

Specifically, from each group of the different cation neutralized highacid ionomer resins set forth in Table 8, the best overall ionomer(based upon C.O.R., melt index and Shore D hardness) was utilized toproduce a number of blends ("diblends" and "triblends") and processed toproduce the cover component of multi-layered golf balls. The "diblends"consisted of 50/50 mixtures and the "triblends" consisted of a33.33/33.33/33.33 mixtures.

With respect to the blends set forth below, Na refers to Formulation No.3, C.O.R. (molded/finished) of 0.812/817; Mn refers to Formulation No.6, C.O.R. (molded/finished) of 0.814/0.814; Li refers to Formulation No.10, C.O.R. (molded/finished) of 0.818/0.819; K refers to Formulation No.13, C.O.R. (molded/finished) of 0.805/0.809; Zn refers to FormulationNo. 16, C.O.R. (molded/finished) of 0.797/0.796; Mg refers toFormulation No. 18, C.O.R. (molded/finished) of 0.814/0.820; Ca refersto Formulation No. 21, C.O.R. (molded/finished) of 0.813/0.812; Nirefers to Formulation No. 28, C.O.R. (molded/finished) of 0.799/0.817;and 50/50 Iotek 8000/7030 refers to control of 50/50 blend of Iotek8000/7030, C.O.R. (molded/finished) of 0.810/0.812. The C.O.R. values ofthe "diblends" and "triblends" were then evaluated after molding with acenter stock having the following composition:

    ______________________________________                                        MATERIAL          WEIGHT (phr)                                                ______________________________________                                        BR-1220.sup.1     70.70                                                       Taktene 220.sup.2 29.30                                                       React Rite ZDA.sup.3                                                                            31.14                                                       Zinc Oxide        6.23                                                        Zinc Stearate     20.15                                                       Limestone         17.58                                                       Ground Flash (20-40 mesh)                                                                       20.15                                                       Blue Masterbatch  .012                                                        Luperco 231XL.sup.4                                                                             .89                                                         or Trigonox 29/40.sup.5                                                       Papi 94.sup.6     .50                                                         ______________________________________                                         .sup.1 BR1220 is high cispolybutadiene from Shell Chemical Co., Houston       Texas.                                                                        .sup.2 Taktene is high cispolybutadiene from Polysar Chemical.                .sup.3 ZDA is zinc diacrylate.                                                .sup.4 Luperco 231XL is a peroxidefree radical initiator manufactured and     sold by Atochem, Buffalo, New York.                                           .sup.5 Trigonox 29/40 is peroxidefree radical initiator manufactured and      sold by Akzo Chemie America, Chicago, Illinois.                               .sup.6 Papi 94 is a polymeric diisocyanate available from Dow Chemical        Co., Midland, Michigan.                                                  

In addition, the molded balls were coated and finished according to theprocedure mentioned above. The C.O.R. values of the finished balls weredetermined in order to evaluate whether any improvement in resiliencewas produced. Generally, it is typical to observe a 0.002 to 0.003 pointpick up in C.O.R. values of the finished balls in comparison to themolded balls. The results are set forth in Tables 9A, 9B and 10 below.

                  TABLE 9A                                                        ______________________________________                                        Diblends (50/50 Blends) C.O.R.                                                (Molded/Finished) Values                                                      Formulation No.                                                                           Blend      C.O.R. (Molded/Finished)                               ______________________________________                                        31          Na/Mn      .813/.818                                              32          Na/Li      .813/.818                                              33          Na/K       .809/.816                                              34          Na/Zn      .811/.818                                              35          Na/Mg      .813/.819                                              36          Na/Ca      .811/.819                                              37          Mn/Li      .811/.817                                              38          Mn/K       .811/.818                                              39          Mn/Zn      .807/.814                                              40          Mn/Mg      .809/.816                                              41          Mn/Ca      .809/.816                                              42          Li/K       .810/.817                                              43          Li/Zn      .813/.819                                              44          Li/Mg      .812/.820                                              45          Li/Ca      .811/.818                                              46          K/Zn       .810/.815                                              47          K/Mg       .811/.820                                              48          K/Ca       .810/.817                                              49          Zn/Mg      .807/.814                                              50          Zn/Ca      .808/.814                                              51          Mg/Ca      .801/.818                                              52          Na/Ni      .809/.815                                              53          Mn/Ni      .807/.814                                              54          Li/Ni      .809/.816                                              55          K/Ni       .809/.816                                              56          Zn/Ni      .799/.804                                              57          Mg/Ni      .805/.813                                              58          Ca/Ni      .807/.815                                              59          Iotek 959/960                                                                            .811/.818                                              60          Control    .809/NA                                                61          Control    .806/NA                                                ______________________________________                                         Controls are Formulation No. 59, a 50/50 blend of Iotek 959/960;              Formulation No. 60 a 75/25 blend of Surlyn 8162/8422; and Formulation No.     61 a 50/50 blend of Iotek 8000/7030.                                     

                                      TABLE 9B                                    __________________________________________________________________________    Synergy Values of the DiBlends                                                Formulation                                                                         Salt                                                                             Salt                                                                             (COR)                                                                             (COR)                                                                             (COR) exp-                                                                          Final Final Final                                   No.   1  2  calc                                                                              exp (COR) calc                                                                          (COR) calc                                                                          (COR) exp                                                                           (COR) Diff.                             __________________________________________________________________________    31    Na Mn 813.0                                                                             813.0                                                                             0.0   815.5 818.0 2.5                                     32    Na Li 815.0                                                                             813.0                                                                             -2.0  818.0 818.0 0.0                                     33    Na K  808.0                                                                             809.0                                                                             1.0   813.0 816.0 3.0                                     34    Na Zn 804.5                                                                             811.0                                                                             6.5   806.5 818.0 11.5                                    35    Na Mg 813.0                                                                             813.0                                                                             0.0   818.5 819.0 0.5                                     36    Na Ca 812.5                                                                             811.0                                                                             -1.5  814.5 819.0 4.5                                     37    Mn Li 816.0                                                                             811.0                                                                             -5.0  816.5 817.0 0.5                                     38    Mn K  809.0                                                                             811.0                                                                             2.0   811.5 818.0 6.5                                     39    Mn Zn 805.5                                                                             807.0                                                                             1.5   805.0 814.0 9.0                                     40    Mn Mg 814.0                                                                             809.0                                                                             -5.0  817.0 816.0 -1.0                                    41    Mn Ca 813.5                                                                             809.0                                                                             -4.5  813.0 816.0 3.0                                     42    Li K  811.0                                                                             810.0                                                                             -1.0  814.0 817.0 3.0                                     43    Li Zn 807.5                                                                             813.0                                                                             5.5   807.5 819.0 11.5                                    44    Li Mg 816.0                                                                             812.0                                                                             -4.0  819.5 820.0 0.5                                     45    Li Ca 815.5                                                                             811.0                                                                             -4.5  815.5 818.0 2.5                                     46    K  Zn 800.5                                                                             810.0                                                                             9.5   802.5 815.0 12.5                                    47    K  Mg 809.0                                                                             811.0                                                                             2.0   814.5 820.0 5.5                                     48    K  Ca 806.0                                                                             810.0                                                                             4.0   810.5 817.0 6.5                                     49    Zn Mg 805.5                                                                             807.0                                                                             1.5   808.0 814.0 6.0                                     50    Zn Ca 805.0                                                                             808.0                                                                             3.0   804.0 814.0 10.0                                    51    Mg Ca 813.5                                                                             810.0                                                                             -3.5  816.0 818.0 2.0                                     52    Na Ni 805.5                                                                             809.0                                                                             3.5   817.0 815.0 -2.0                                    53    Mn Ni 806.5                                                                             807.0                                                                             0.5   815.5 814.0 -1.5                                    54    Li Ni 808.5                                                                             809.0                                                                             0.5   818.0 816.0 -2.0                                    55    K  Ni 801.5                                                                             809.0                                                                             7.5   813.0 816.0 3.0                                     56    Zn Ni 798.0                                                                             799.0                                                                             1.0   806.5 804.0 -2.5                                    57    Mg Ni 806.5                                                                             805.0                                                                             -1.5  818.5 813.0 -5.5                                    58    Ca Ni 806.0                                                                             807.0                                                                             1.0   814.5 815.0 0.5                                     __________________________________________________________________________

In Table 9B above, the C.O.R. synergy values are based upon the datafrom Table 8 of the various metal cation neutralized high acid acrylicacid based ionomer resins and the following calculations:

(COR)calc=coefficient calculated as weighted average of as-molded COR'sfor polymers of salts 1 and 2

(COR) exp=experimental as-molded COR for blend FINAL(COR)calc=coefficient calculated as weighted average of finished COR'sfor polymers of salts 1 and 2

FINAL (COR) exp=experimental finished COR for blend

FINAL (COR) diff=difference between FINAL (COR) exp and FINAL (COR)(calc)

As noted in Table 9B, positive synergy in resilience is observed fornearly all of the finished (final) blends, with substantial synergybeing produced in Formulation Nos. 34, 38, 39, 43, 46, 48, 49, 50.

Moreover, the diblends were also evaluated against a control FormulationNo. 59 (see Table 9A) , a 50/50 blend of Iotek 959/960, the bestavailable high acid blends, with respect to improved C.O.R. values (i.e.811/0.818). Similar or enhanced C.O.R. values (molded/finished) wereobserved in Formulation Nos. 31 (Na/Mn), 32 (Na/Li), 34 (Na/Zn), 35(Na/Mg), 36 (Na/Ca) , 38 (Mn/K), 43 (Li/Zn), 44 (Li/Mg), 45 (Li/Ca), and47 (K/Mg).

Furthermore, when reviewed for cold cracking, with the exception ofFormulation No. 35, all of the diblends tested exhibited resistance tobreaking. With respect to Formulation No. 35, some breakage did occurwith 2 out of the 12 balls tested exhibiting breakage.

When the small test sample of the triblends were evaluated (see Table 10below) in comparison to a 50/50 blends of the low acid acrylic acidbased hard ionomers (i.e. Iotek 8000/7030 U.S. Pat. No. 4,911,451), allof the cation neutralized high acid acrylic acid based triblendsproduced enhanced C.O.R. values upon molding and finishing. In addition,when subjected to cold cracking, no breakages were observed.

                  TABLE 10                                                        ______________________________________                                                                 C.O.R.  C.O.R.                                       Formulation                                                                             Cation Blend   Molded  Finished Ball                                ______________________________________                                        62        Zn/Li/K        .819    .828                                         63        Na/Zn/Li       .821    .829                                         64        Iotek 8000/7030                                                                              .816    .819                                         65        Na/Mn/Ca       .820    .828                                         66        Na/K/Mn        .821    .829                                         67        Na/K/Mg        .821    .829                                         ______________________________________                                    

Consequently, not only are a number of new cation neutralized acrylicacid based high acid ionomers now available for golf ball coverconstruction, these new cation neutralized acrylic acid based high acidionomers may be blended together in various combinations to producecover compositions exhibiting enhanced resilience (i.e. distance) due tothe synergies noted above.

Example 2

In order to determine whether the diblends or triblends of the newcation neutralized acrylic acid based high acid ionomer resins produceddifferent results when dry blended (i.e. prepared as simple dry blendsof pre-made single cation neutralized acrylic acid based high acidionomers, such as those set forth in Example 1 above) or when producedas "in-situ" cation blends (i.e. the cations were first blended and thenadded to the acrylic acid/ethylene copolymers in the Banbury mixer), anumber of comparison reactions were generated. Specifically, in-situFormulation Nos. 68-72 in Table 11 below correspond to dry-blendedFormulation Nos. 31, 32, 43, 44 and 46, respectively, and in-situFormulation Nos. 73 and 74 in Table 11 below correspond to dry-blendedFormulation Nos. 62 and 63, respectively.

                  TABLE 11                                                        ______________________________________                                                                    C.O.R.                                                                              Spin Rate                                                                            Shore D                                         Cation   C.O.R.  Fin-  9-Iron,                                                                              Hard-                                Formulation No.                                                                          Blend    Molded  ished RPM    ness                                 ______________________________________                                        68         Na/Mn    .822    .828  5,008  74                                   69         Na/Li    .820    .828  5,820  70                                   70         Li/Zn    .820    .825  5,425  71                                   71         Li/Mg    .821    .828  5,451  73                                   72         Zn/K     .817    .821  5,934  69                                   73         Li/Zn/K  .822    .826  5,266  71                                   74         Na/Li/Zn .821    .824  5,165  71                                   75         Iotek    .819    .824  5,926                                                  959(Na)/                                                                      960(Zn)                                                            Tour Edition ® 100            10,124                                      Tour Edition ® 90             9,821                                       Top-Flite ® XL II             6,942                                       ______________________________________                                    

The results indicated that little difference in C.O.R. was produced(relative to a control of 50/50 mixture of the high acid Iotek 959/960)whether a dry blending process or an in-situ blending process was used.Moreover, the data further clearly indicated that the cation neutralizedacrylic acid based high acid ionomer blends of the present inventiongenerally exhibit higher C.O.R. values and significantly lower spinrates than the best acrylic acid based high acid ionomers (i.e. theIoteks 959(Na)/960(Zn) blend), see Formulation Nos. 68, 70, 71, 73 and74 in comparison to Formulation No. 75 (control). The lower C.O.R. valueand the substantially similar spin rate produced by the Zn/K blend inFormulation 72 was attributed to the slightly lower hardness of thisblend versus the others. As indicated in Table 8, the K and Zn acrylicacid based high acid ionomers are a little softer than the Na, Mn, Liand Mg acrylic acid based high acid ionomers. Similarly, the higher spinrate of the Na/Li blend in Formulation 69 was due to its relativesoftness versus the other blends. In addition, other more subtle factorsmay also be at play, such as differences in coefficient of friction,deformation under load, etc., which have not quantified.

In addition, when compared with a number of commercially available ballsproduced by Spalding & Evenflo Companies, Inc., the assignee of thepresent invention, with low acid ionomer resin covers (i.e. the TourEdition® 100, Tour Edition® 90 and Top-Flite® XL II balls), the spinrates of the cation neutralized acrylic acid high acid ionomer blends ofthe present invention (i.e. Formulations 68-75) exhibited much lowerspin rates. Consequently, the cation neutralized acrylic acid based highacid ionomer blends of the present invention produced, when utilized toformulate the cover of a multi-layered golf ball, a much harder surfacethen those produced by the low acid ionomer covers presently available.This may be desirable to a golfer who imparts unmanageable spin(slice/hook) to the ball and therefore may benefit from a "low spin"ball.

Example 3 Acrylic Acid Based High Acid Ionomer Di-Blends ContainingVarying Ratios of Cation Neutralized Acrylic Acid Based High AcidIonomers

In addition to the 50/50 blends of various combinations of the newcation neutralized acrylic acid based high acid ionomers set forth inExample 1, di-blends varying from 25/75 to 75/25 ratios were producedutilizing the more preferred diblends in the "in-situ" process describedin Example 2. In this regard, the more preferred diblend formulationsset forth in Example 1 (i.e. Formulation No. 31 (Na/Mn), Formulation No.32 (Na/Li), Formulation 43 (Li/Zn), Formulation No. 44 (Li/Mg), andFormulation No. 46 (Zn/K)) were produced in-situ in 50/50 so, 25/75 and75/25 combinations according to the following formulations:

                                      TABLE 12                                    __________________________________________________________________________    Formulations                                                                  __________________________________________________________________________    Ingredients                                                                            76 77 78 79 80 81 82 83 84 85                                        __________________________________________________________________________    Acid     100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                       Copolymer                                                                     (Primacor                                                                     5981)                                                                         NaOH     2.0                                                                              1.0                                                                              3.0                                                                              2.0                                                                              1.0                                                                              3.0                                                                              -- -- -- --                                        Mn Acetate                                                                             15.0                                                                             22.5                                                                             7.5                                                                              -- -- -- -- -- -- --                                        Lithium  -- -- -- 3.1                                                                              4.7                                                                              1.6                                                                              3.1                                                                              1.6                                                                              4.7                                                                              3.1                                       Hydroxide                                                                     Monohydrate                                                                   Zinc     -- -- -- -- -- -- 8.00                                                                             12.0                                                                             4.0                                                                              --                                        Acetate                                                                       Potassium                                                                              -- -- -- -- -- -- -- -- -- --                                        Hydroxide                                                                     Magnesium                                                                              -- -- -- -- -- -- -- -- -- 10.5                                      Acetate                                                                       __________________________________________________________________________                  Formulation No.                                                 Ingredients   86   87   88   89   90                                          __________________________________________________________________________    Primacor 5981 100  100  100  100  100                                         Lithium Hydroxide                                                                           1.6  4.7  --   --   --                                          Magnesium Acetate                                                                           15.8 5.3  --   --   --                                          Zinc Acetate  --   --   8.00 12.0 4.0                                         Potassium     --   --   4.50 2.25 6.75                                        Hydroxide                                                                     __________________________________________________________________________

The di-blends produced the following C.O.R. values:

                  TABLE 13                                                        ______________________________________                                        Formulation No.                                                                              Cation Blend                                                                            C.O.R. (Molded)                                      ______________________________________                                        76             50/50 Na/Mn                                                                             .820                                                 77             25/75 Na/Mn                                                                             .821                                                 78             75/25 Na/Mn                                                                             .825                                                 79             50/50 Na/Li                                                                             .822                                                 80             25/75 Na/Li                                                                             .822                                                 81             75/25 Na/Li                                                                             .823                                                 82             50/50 Li/Zn                                                                             .816                                                 83             25/75 Li/Zn                                                                             .804                                                 84             75/25 Li/Zn                                                                             .825                                                 85             50/50 Li/Mg                                                                             .823                                                 86             25/75 Li/Mg                                                                             .822                                                 87             75/25 Li/Mg                                                                             .821                                                 88             50/50 Zn/K                                                                              .820                                                 89             75/25 Zn/K                                                                              .798                                                 90             25/75 Zn/K                                                                              .821                                                 ______________________________________                                         Control is a 50/50 Iotek Low Acid Ionomer Blend 8000/7030), C.0.R.            (molded) .817                                                            

The results indicated that in general the new cation neutralized acrylicacid based high acid ionomer diblends produced enhanced C.O.R. valuesover the known acrylic acid based low acid ionomer blends. SeeFormulation Nos. 76-81, 84-88 and 90. While Formulation 82 produced alower C.O.R. value than expected, the data suggested that in some cases,a 50/50 blend is not optimal (particularly in the Zn/K and the Li/Znblends), while in others (i.e. Li/Mg, Na/Li) the blend ratio is notsignificantly different.

Example 4

Since the data set forth in Examples 1-3 indicated the resilience(C.O.R.) and/or hardness properties of the cover compositions can besubstantially enhanced through the use of the new cation neutralizedacrylic acid based high acid ionomers and/or diblends or triblends ofsuch ionomers, the molecular weight property of the acrylicacid/ethylene copolymers utilized to produce the ionomers was evaluated.Specifically, the molecular weight of the acid copolymers was assessedfor the purpose of determining whether further enhanced properties canbe produced by varying the molecular weight of the acid copolymer.

In this regard, since the data indicated that there was littledifference between using the dry blending process or the in-situblending method for processing the cations, the in-situ method ofproducing the cation neutralized high acid ionomer blends was used inthis analysis.

Along this line, the diblend and triblends set forth in Formulation Nos.68, 73 and 74 are essentially the same as those set forth below inFormulation Nos. 91, 94 and 97, respectively. However, since a differentbatch of cores was utilized than those used in Example 2, the C.O.R.'sare slightly lower. While the cores utilized in the present Example wereof the same composition, the lower C.O.R. was due to the age of thecores, i.e. molded cores will lose C.O.R. upon aging mainly due tomoisture pickup. Formulation Nos. 92-93, 95-96 and 98-99, are similar tothose set forth in Formulation Nos. 91, 94 and 97, respectively, withthe exception that the molecular weight of the acrylic acid/ethylenecopolymer utilized was varied. Specifically, Primacor 5983 and Primacor5990 both contain the same acid content as Primacor 5981 (i.e. 20 weightpercent acrylic acid) but have lower viscosities (lower molecularweights) and lower densities. Primacor 5981 has a melt index of 300 g/10minute (ASTM Method D-1238 at 190° C.) and a Brookfield viscosity of51,000 cps at 350° F. Primacor 5983 has a melt index of 500 and aBrookfield viscosity of 26,000 cps at 350° F.; and Primacor 5990 has amelt index of 1300 and viscosity of 13,000 cps at 350° F.

The resilience (C.O.R.) of the molded balls produced utilizing thedifferent molecular weight acrylic acid/ethylene copolymers are setforth below in Table 14.

                  TABLE 14                                                        ______________________________________                                        Formulation No.                                                                         Cations   Acid Copolymer                                                                            C.O.R. (MOLDED)                               ______________________________________                                        91        Na/Mn     Primacor 5981                                                                             .813                                          92        Na/Mn     Primacor 5983                                                                             .805                                          93        Na/Mn     Primacor 5990                                                                             All Balls crack                               94        Li/Zn/K   Primacor 5981                                                                             .814                                          95        Li/Zn/K   Primacor 5983                                                                             .809                                          96        Li/Zn/K   Primacor 5990                                                                             All Balls crack                               97        Na/Li/Zn  Primacor 5981                                                                             .813                                          98        Na/Li/Zn  Primacor 5983                                                                             .808                                          99        Na/Li/Zn  Primacor 5990                                                                             All Balls crack                               ______________________________________                                    

The data indicated that a higher molecular weight acid copolymer ispreferred for obtaining high resilience (i.e. C.O.R.) and requiredtoughness.

Example 5

By way of further example, golf ball cover compositions were prepared byfirst blending an acid copolymer such as ethylene acrylic acid copolymer(EAA) with a non-acid functional polymer such as ethylene-ethyl acrylate(EEA) and/or ethylene-methyl acrylate (EMA). This was followed byaddition of a cation or cation blend for neutralization. Selection ofthe type and ratio of acid copolymer to EEA or EMA was based upon thedesired final properties of the ball such as hardness or spin rate.Tables 15-17 show the compositions and properties of balls having coversprepared using ethylene acrylates, and Table 18 shows the properties ofseveral golf balls produced by the present assignee which do not containethylene acrylates but exhibit somewhat similar properties.

Table 15 below provides for the results of simple blends of ionomerswith various non-acid functional polymers. Iotek's 959 and 960 wereselected for their similarity in properties to ionomers made fromPrimacor 5981.

                  TABLE 15                                                        ______________________________________                                        Formulation                                                                   No.      100    101    102  103  104  105  106  107                           ______________________________________                                        Iotek 959                                                                              50     25     25   25   25   25   25   25                            Iotek 960                                                                              50     25     25   25   25   25   25   25                            Kraton   --     50     --   --   --   --   --   --                            FG-1901X                                                                      EEA 6169 --     --     50   --   --   --   --   --                            EEA 6182 --     --     --   50   --   --   --   --                            EMA 53.04                                                                              --     --     --   --   50   --   --   --                            EMA XS 12.04                                                                           --     --     --   --   --   50   --   --                            EMA TC-130                                                                             --     --     --   --   --   --   50   --                            Fusabond --     --     --   --   --   --   --   50                            D-197                                                                         Compression                                                                            56     59     61   60   61   61   63   60                            Molded COR                                                                             .818   .797*  .797 .798 .797 .798 .793*                                                                              .796                          Finished .821   .798   .795 .798 .797 .799 .787 .796                          COR                                                                           Shore C  98     85     86   88   80   85   80   88                            Hardness                                                                      Cut Resistance                                                                         4-5    3      2-3  2    2    2    2    2                             Spin Rate (full                                                                        5,969  9,495  8,997                                                                              9,260                                                                              9,145                                                                              9,732                                                                              9,857                                                                              9,340                         9 iron)                                                                       ______________________________________                                         *Several balls cracked on Formulations 101 and 106 during COR testing.   

Blends similar to those of Table 15 were prepared using Primacor 5981 asthe acid copolymer of choice instead of Iotek 959/960. These blends, andthe resulting properties, are set forth below in Table 16:

                  TABLE 16                                                        ______________________________________                                        Formulation                                                                   No.     108    109    110  111  112   113  114  115                           ______________________________________                                        Primacor                                                                              100    50     50   50   50    50   50   50                            5981                                                                          Nucrel 960                                                                            --     --     --   --   --    --   --   --                            Kraton  --     50     --   --   --    --   --   --                            FG-1901X                                                                      EEA 6169                                                                              --     --     50   --   --    --   --   --                            EEA 6182                                                                              --     --     --   50   --    --   --   --                            EMA 53.04                                                                             --     --     --   --   50    --   --   --                            EMA     --     --     --   --   --    50   --   --                            X512.04                                                                       EMA     --     --     --   --   --    --   50   --                            TC-130                                                                        Fusabond                                                                              --     --     --   --   --    --   --   50                            D-197                                                                         Zinc    5.33   5.33   5.33 5.33 5.33  5.33 5.33 5.33                          Acetate                                                                       Potassium                                                                             3.00   3.00   3.00 3.00 3.00  3.00 3.00 3.00                          Hydroxide                                                                     Lithium 2.05   2.05   2.05 2.05 2.05  2.05 2.05 2.05                          Hydroxide                                                                     Compression                                                                           55     62     60   60   63    63   62   62                            Molded  .820   .802   .792 .794 .791  .790 .793 .802                          COR                                                                           Finished                                                                              .825   .802   .792 .796 .793  .790 .794 .801                          COR                                                                           Shore C 98     90     86   90   77    83   83   88                            Hardness                                                                      Cut     4-5    3      3    3    2     3    2    3-4                           Resistance                                                                    Spin Rate                                                                             5,787  8,834  9,232                                                                              9,148                                                                              10,220                                                                              9,516                                                                              9,552                                                                              9,091                         (Full 9 Iron)                                                                 ______________________________________                                    

While Primacor 5981 has been the acid copolymer of choice herein as aresult of its high COR, it should be noted that lower acid copolymers ora blend of acid copolymers may be used with satisfactory results. Table17 below shows several compositions using lower acid copolymers or ablend of acid copolymers, along with the resulting properties of thefinished cover and ball.

                  TABLE 17                                                        ______________________________________                                        Formulation No.                                                                           116      117     118   119   120                                  ______________________________________                                        Primacor 5981                                                                             --       --      --    25    --                                   Nucrel 960  50       50      50    25    100                                  Kraton FG-1901X                                                                           --       --      --    --    --                                   EEA 6169    --       --      --    --    --                                   EEA 6182    50       --      --    --    --                                   EMA 53.04   --       50      --    50    --                                   EMA X512.04 --       --      --    --    --                                   EMA TC-130  --       --      --    --    --                                   Fusabond D-197                                                                            --       --      50    --    --                                   Zinc Acetate                                                                              4.00     4.00    4.00  4.70  4.00                                 Potassium Hydroxide                                                                       2.27     2.27    2.27  2.60  2.27                                 Lithium Hydroxide                                                                         1.50     1.50    1.50  1.80  1.50                                 Compression 68       66      64    64    58                                   Molded COR  .793     .789    .800  .790  .813                                 Finished COR                                                                              .793     .788    .798  .790  .815                                 Shore C Hardness                                                                          86       75      88    76    96                                   Cut Resistance                                                                            3        3       3     3     4                                    Spin Rate (Full 9 Iron)                                                                   9,436    10,306  9,315 10,168                                                                              7,014                                ______________________________________                                    

One of the objectives in preparing the formulations listed in Tables15-17 was to make a soft covered golfball having properties similar tothe current "Tour" balls of the present assignee. The properties of thesubject assignee's Titleist Tour 100, Tour Edition 100, Tour Edition 90,and Top-Flite XL II are provided in Table 18. These properties may becompared with those listed in Tables 15-17 to find many similaritiessuch that a lower cost alternative may be provided.

                  TABLE 18                                                        ______________________________________                                                          Tour     Tour     Top-                                                Titleist                                                                              Edition  Edition  Flite XL                                            Tour 100                                                                              100      90       II                                        ______________________________________                                        Compression 75        57       55     47                                      Molded COR  --        --       --     --                                      Finished COR                                                                              .786      .809     .813   .814                                    Shore C Hardness                                                                          82        84       86     96                                      Cut Resistance                                                                            1         3        3      4-5                                     Spin Rate (Full 9 Iron)                                                                   9,422     9,924    9,703  6,968                                   ______________________________________                                    

Little is known of the reaction mechanism or to what extent the EEAand/or EMA actually take part in the reaction of EEA/EMA with an acidcopolymer and the addition of a cation or cation blend forneutralization. There is, however, some belief that there is at leastenough interaction between polymers to provide a net benefit inproperties versus a simple blend of an ionomer and EEA/EMA. It ispossible that an interpenetrating polymer network (IPN) is formed byreacting (neutralizing) the acid copolymer in the presence of EEA/EMA.By first forming an intimate blend of polymers and then neutralizing onein the presence of another it is possible that a network is formed viaintermolecular chain entanglement of the two polymers.

It is also possible that a dynamic vulcanization takes place wheresuperior properties are the result of a finer phase morphology of thedispersed crosslinked phase (here, the neutralized acid copolymer) in anessentially uncrosslinked continuous matrix of ethylene acrylate ester.

The formations of Tables 15-17 above include examples of an acidcopolymer reacted in the presence of maleic anhydride functionalelastomers Kraton FG-1901X and Fusabond D-197. In simple blends withionomers, this was the subject of U.S. Pat. Nos. 4,986,545 and5,098,105, incorporated herein by reference.

A further advantage of the reactive blends of Tables 16 and 17 over thenon-reactive blends of Table 15 is the improved cut resistance. Whilemost of the blends of Table 15 give an undesirable "2" rating, nearlyall of those in Tables 16 and 17 give a rating of "3", which iscomparable to the current Tour balls (see, e.g. Table 18). It should befurther noted that formulations 101 and 106 in Table 15 had severalballs break during COR testing. The related formulations in Table 16(formulations 109 and 114) did not have this problem. In general,although no COR advantage is observed (i.e., some COR values of Table 16are higher and some are lower than the corresponding Table 15formulations) the balls prepared using the formulations of Table 16 aretougher, slightly softer and more durable than those of Table 15.

The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon a reading and understanding of the preceding detaileddescription. It is intended that the invention be construed as includingall such alterations and modifications insofar as they come within thescope of the appended claims or the equivalents thereof.

We claim:
 1. A golf ball having a core and a cover wherein said covercomprises about 30 to 90 parts by weight of an unneutralized acidcopolymer and about 10 to 70 parts by weight of an ethylene copolymerincluding up to about 30% by weight of an alkyl acrylate and aneutralizing metal cation wherein the unneutralized acid copolymer isneutralized by the metal cation in the presence of the ethylenecopolymer and the alkyl acrylate.
 2. A golf ball, as set forth in claim1, wherein the cover comprises about 40 to 80 parts by weight of an acidcopolymer and about 20 to 60 parts by weight of an ethylene copolymer.3. A golf ball, as set forth in claim 1, wherein the cover comprisesabout 50 to 70 parts by weight of an acid copolymer and about 30 to 50parts by weight of an ethylene copolymer.
 4. A golf ball, as set forthin claim 1, wherein the acid copolymer includes about 1 to about 25% byweight of an alpha, beta unsaturated carboxylic acid.
 5. A golf ball, asset forth in claim 1, wherein the acid copolymer includes about 16% toabout 25% by weight of an alpha, beta unsaturated carboxylic acid.
 6. Agolf ball, as set forth in claim 1, wherein the ethylene copolymer isethylene ethyl acrylate.
 7. A golf ball, as set forth in claim 1,wherein the ethylene copolymer is ethylene methyl acrylate.
 8. A golfball, as set forth in claim 1, wherein the ethylene copolymer isethylene butyl acrylate.
 9. A golf ball, as set forth in claim 1,wherein the acid copolymer is an acrylic acid/ethylene copolymercomprising about 20% acrylic acid.
 10. A golf ball, as set forth inclaim 1, further including up to about 11 parts by weight of an acetateor hydroxide salt of a member selected from the group consisting ofzinc, potassium, lithium, calcium, sodium, nickel, magnesium, andmanganese, said acetate or hydroxide salt providing a source for theneutralizing metal cation.
 11. A golf ball having a core and a coverwherein the cover comprises a composition including an unneutralizedacid copolymer including about 9% to about 25% acrylic acid, and anethylene copolymer including up to about 30% by weight of an alkylacrylate selected from the group consisting of methyl acrylate, butylacrylate, and ethyl acrylate, the acid copolymer comprising about 30 to90 parts by weight of the overall composition and the ethylene copolymercomprising 10 to 70 parts by weight of the composition, the coverfurther including a metal salt of a member selected from the groupconsisting of zinc, potassium, lithium, calcium, sodium, nickel,magnesium, and manganese wherein the unneutralized acid copolymer isneutralized by the metal salt in the presence of the ethylene copolymerand the alkyl acrylate.
 12. A golf ball comprising a core and a cover,said cover comprising:about 30 to 90 parts by weight of an acidcopolymer including about 1% to 25% parts by weight unneutralizedcarboxylic acid such that about 10 to 90% of the carboxyl groups areneutralized with a metal cation; and about 10 to 70 parts by weight ofan ethylene copolymer including up to about 30% by weight of an alkylacrylate wherein the unneutralized acid copolymer is neutralized by themetal cation in the presence of the ethylene copolymer and the alkylacrylate.
 13. A golf ball, as set forth in claim 12, wherein thecarboxylic acid is acrylic acid.
 14. A golf ball, as set forth in claim12, wherein the metal cation is selected from the group consisting ofzinc, potassium, lithium, calcium, sodium, nickel, magnesium, andmanganese.
 15. A golf ball, as set forth in claim 12, wherein the alkylacrylate is selected from the group consisting of butyl acrylate, methylacrylate, and ethyl acrylate.
 16. A golf ball, as set forth in claim 12,wherein the cover comprises about 40 to 80 parts by weight of an acidcopolymer and about 20 to 60 parts by weight of an ethylene copolymer.17. A golf ball, as set forth in claim 12, wherein the cover comprisesabout 50 to 70 parts by weight of an acid copolymer and about 30 to 50parts by weight of an ethylene copolymer.